Yep, that's pretty much it.He might be arguing that the payment benefits
Trump, & is therefore a campaign contribution.
This would be a very tortured argument, but the
rampant hatred encourages such thinking.
Campaign contribution laws are, necessarily, pretty complex. I don't claim to be anything resembling an authority. But the most plausible explanation I have heard, so far, for why a lawyer took claim for the payment was because if campaign funds were used it was definitely a violation of the law. You can't just use campaign funds for anything.
Maybe it's really nothing. Maybe not. But Trump isn't exactly Mr. Transparent. He has a history of buying his way out of legal problems.
Tom